The behavior does not change by altering the VM configuration as long it is a generation-2 Hyper-V with 2.6.32-696 kernel series.The Centos 6.8 kernel minimal iso kernel kernel 2.6.32-642.el6.x86_64 kernel boots without any issue.Centos 2.6.32-696 kernel series does not have that issue withand Hyper-V Generation-1 vms.

The Hyper-V Generation-2 VM is configured with 8192 MB of ram, 4 Virtual processors, one scsi contoller with a dynamic expanding 127 Gib virtual disk at position 0 and one cdrom at position 1.

The behavior does not change by altering the VM configuration as long it is a generation-2 Hyper-V with 2.6.32-696 kernel series.

Even if you remove the CD drive from the VM? All your waits seem to be something to do with it... perhaps just insert some media in it and see if that helps.

Thank you TrevorH,I removed the virtual scsi cdrom drive and all the pauses are gone. Now Centos 6.9 booted at 8 seconds.I checked the Centos 6.8 kernel logs more thoroughly and there are a couple of the following messages: